Method of mining



E. C. MORGAN.

METHOD OF MINING.

APPLICATION FILED OCT.26. 1917.

' 1,330,741. Patented Feb. 10, 19,20.

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WITNE88E8: IL 2 9 INVENTOI? Coal E. C; MORGAN.

METHOD OF MINING. 1 APPLICATION FILED ocnzs. 1911.

' Patented Feb. 10,1920.

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E. C. MORGAN.

METHOD OF MINING APPLICATION FILED ocnzs. 1911.

30,741 Patented Fb. 10,1920.

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EDMUND. C. MORGAN, OE YORK, N. Y.

ivrn'rnonor MINING.

A'pplicationfiled October 26, 1917.

To all whom it may concern.

Be it known that I, EDMUND C. MORGAN, a citizen ofthe United States, residing at Richmond Hill, New York city, county of Queens, and State ot'New York, have invented anew and useful-h lethod ot Mining, of which the following is a specification.

The objects-of my invention are conservation of the minerals in the earth, the forests, and the surface of the earth" above mining operations; a greater degree of safety to mine operatives, and cheapening the cost of mmlng.

I attain these objects by the method and apparatus for same illustrated in the accoIn-' panying three sheets of drawings, of which Figures 1, 2, 3, l, 5, 6, 7 and 8 are illustrative of the method, and Figs. 9, 10, 11, 12. trative of the apparatus, which I have described and'claimed in my copending application Ser. No. 178,766, filed July 5, 1917, for an improvement in apparatus for min inn root props.

The sameletters and figuresrefer to like par throughout the several views.

Generally speaking, mining and especially coal mining in the United States is now carried on in a very wasteful way. The coal deposits are so vast and so widely distributed that competition is very keen, therefore only the best grades of coal contained in the easiest and cheapest veins to mine are worked. This in itself would not beso bad, but owing to the pi sent method-of mining, it results in the distortion and ruin of the veins of coal above, and loss even of much of the coal in the vein being worked.

Simply stated. the main features of min ing as now carried on are, the removal of the mineral and the subsidence of the overlying strata. The ideal method as 'far as the vein being worked isconcerned, is by what is known as the longwall system of Specification of Letters Patent.

13, ii, 15, 16, 17, isand 19 are illus-- PatentedFeb. 10, 1920.

Serial No. 198,746.

country is now carried on by what isknown as the room and pillar system, which, in most cases, is exceedingly wasteful of the coal in the vein being worked, destructive to'the veins in the overlying strata and the land at the surface, and in addition requires a large amount of timbering to support the roof long enough to get what coal is obtained, so that in-the aggregate avast forest is disappearing into the mines every year, and in addition to all this the fatalities each year caused by falls from the breaking root are more than from all other causes combined, even including the terrible gas and dust explosions that occur from time to time.

By the use of my methods of supporting mine roots, the best method of mining can becarried on in thick as well as thin veins, practically all of the mineral is saved in the vein being worked. and none of the mineral in the strata above, or the land at the surface disturbed, and this, with a much greater degree of safety to the operatives than with the present method.

I am not as familiar with metal mining as 1 am wi 11 coal mining, but as the main problem in metal mining as well as in coal mining is holding the roof while the mineral is being removed, I believe my method will be very useful in many metal mines.

The character of the strata immediately overlying coal is usually slate or sandstone. and is harder and more able to sustain great weight than the strata immediately linden lying the coal, which is usually fireclay or shale. Sometimes, however, the conditions stated are reversed, and the coal lll have a sandstone or limestone floor and a comparatively-soft roof.

My method of supportlng mine roofs consists in removing wedge, cone, or pyramid shaped sections, in one piece from either the roof or floor, of a height approximately the same as the distance between the floor and root, and placing them at points adjacent to where the sections have'been removed. The height the sections are made is just enough less than the height between floor and root to permit their being moved to the point desired, making allo'vance for uneveninss of floor and root. Ordinarily this is all that will be required, as, owing to the shape of the sections, their height before rcmoval can be determined so that they will be practically tight, and the roof will come to a firm bearing with such a slight movement that it will not crack or cause any appreciable disturbance above. However, if desired, it is entirely practical to drive thin wedges in the slight clearance space, so that heavy pressure even will be applied between floor and roof at each section as soon as it is placed. To make it clear how the sections can be fitted closely between floor and roof I might state that the operative can determine just where he wants to place a section before he removes it, and, with suitable extensible measuring means, can decide just what height he wants the sec tion to be, and owing to the wedge like shape of the section it can be broken off at almost exactly the predetermined point.

The number of sections necessary to be used for a given area will of course vary greatly, owing to the weight of the overlying strata, the material of which the sections are taken, the material of the floor, etc., but it can all be figured with accuracy by those skilled in the art. It is my own idea that sufiicient sections should be used to hold the roof indefinitely, so that it may be practical to work the coal veins that may be in the overlying strata hundreds of years hence.

Referring to the drawings, Fig. 1 is a sectional view through a coal mine including part of the roof and floor. In this case the roof is composed of much stronger material than the floor, therefore the sections are taken from the roof. The cone-shaped section 25 is shown just ready to be removed to a position similar to section 26 which has been placed in its permanent position. Ordinarily the sections will break at the line 2'? Owing to the fact that it is the smallest and weakest section, but if in some material a section does not break of its own weight, a wedge 30 or other similar means may be used to assist in breaking. The thin wedges 28 and 29 may be used as shown, if desired, but the space that need be left between the top of the section 26 and the roof will be much less in proportion than that shown in the drawings, as, owing to the smallness of the scale, the drawings had to be distorted in order to show any wedges at all.

Then a section has been severed from the roof, I prefer to let it down slowly, but it may be allowed to drop quickly, if desired. I see no very serious objection now to doing this, eXcept the rush of air might cause a disagreeable dust. After a section as 25 has been lowered to the floor, it is moved by any suitable means, such as a winding engine of ordinary and well-known construction, as indicated by Fig. 4.

In a great many mines no props of any kind need be regularly used, although the use of removable props as indicated by 31 would not interfere with the application of my invention.

Fig. 2 is a cross section through a coal mine, including a portion of the roof and floor. 111 this case the material of the floor is much stronger than the material of the roof, therefore the sections are taken from the floor. In this view 40'shows a section before removal and 41 shows a section that has been placed in its permanent position. A wedge 42 or other suitable means may be used to cause the section to break at a predetermined point as indicated by line 43. 44 indicates a removable prop that may be used if desired. 45 and 46 indicate thin wedges that may be used the same as de scribed with reference to Fig. 1.

Fig. 3 shows my method applied to a very steep pitching vein, in which 47 indicates a cone-shaped section before removal from the roof, and 48 shows a section in permanent place. 49 and 50 indicate thin wedges that may be used, as described in Fig. 1, in this case the sections being properly guided will find position by their own weight.

Fig. 4 is a plan view of a section of a mine showing a convenient arrangement for moving the dislodged sections of material into place after they have been lowered from the roof to the floor of the mine chamber and for lifting and placing the dislodged sections into desired position, such sections having been taken from the floor of the mine chamber. This arrangement consists of a suitable winding drum 51, an electric motor 52 mounted on a suitable frame 53 which is adapted to slide on the floor of the mine and be anchored in any suitable way such as by means of the anchor 54. A boom 55 and sling rope 56 may be mounted on the frame 53 and arranged to be operated by the electric motor 52. The purpose of this construction is to lift sections of material from the floor and place them in proper position. The draft rope 57 which extends from the winding drum 51 is carried around a pulley connected to an anchor in the mine and then extends around another pulley which may be anchored by the sections 58 and 59 already in roof-propping position between the floor and roof. The end of the rope 57 may be formed into a 100p 60 which surrounds the section of material which is to be moved. Suitable clamps 61, 62 and 63 may be attached to the loop 60 at the end of the rope 57 These clamps, as shown in Fig. 19, may be hook shaped at their lower ends to engage the lower edge of the section of material being moved and prevent the rope loop 60 from moving to the top of the said section of material being moved.

Figs. 5, 6 and 7 show respectively wedge, cone and pyramid shaped sections.

64 indicates the frame of apparatus that may be used to remove the sections from the roof. It is merely put in to show how it can be removed by the winding engine, the rope 57 being shown in dotted line attached to it.

Particular attention is called to Fig. 8, which isa diagrammatic View of a mine showing a number-of sectionsin place. It

will be noted that the air spaces left be tween the sections-are diamond-shaped, and therefore arch upwardly and downwardly; this would be the case whether the sections were taken from the roof or floor, thus always forminga structure of great strength to resist the immense crushing strain.

Figs. 9, 10 and 11 illustrate apparatus for facilitating the removing of cone-shaped sections from the roof, or from the floor by slight modification, as will be referred to further along. Fig. 10, is a top view of the apparatus, and Fig. 9 is composed of several views of Fig. 10. That part bounded by lines indicated by G, H, I, J, is a cross section of Fig. 10 taken on thedotted line, A, B, looking in the direction indicated by the arrow. That part bounded by the lines H, I, L, K, is a section of Fig. 10, taken on dotted line E F, looking in the direction indicated by the arrow, and that part bounded by the lines K, L, M, is a view, not sectional, taken on line C, D of Fig. 10, looking in the direction indicated by the arrow. Fig. 11 is a cross section taken on dotted line N, O, of Fig. 10, looking in the direction indicated by the arrow. The main frame 7 5, Figs. 9, 10 and 11, is in general form the shape of about a threequarter segment of a circle. Revolubly mounted in the main frame 75 by means of a suitable groove bearing, is the frame 76, which is also in general form the shape of about a three-quarter segment of a circle, and has suitable gear teeth formed in its outer edge. Arranged to mesh with the gear teeth on frame 7 6 are the pinions 77 and 80, (Figs. 10 and 11) which are secured to the shafts 78 and 79' carried in suitable bearingsin the main frame 75. Secured to the shafts 78 and 79, are the worm gears 81 and 82', which mesh with worms 83 and 84:, which are suitably secured to the shaft 85, which is carried in suitablebearings S6 and 87 in the main frame 75. A suitable electric motor, 88, is mounted in the main frame, 75, and arranged to drive the shaft 85, by means of gears 89 and 90. Mounted in the frame 76' by means of a suitablestandard 91, is reciprocating tool of well known construction, the one shown:

being operated by electricity." It is slidably mounted in a frame 93, and arranged for feeding movement either by hand or power. The tool frame is provided with a suit able standard 94, and is arranged for universal adjustment by suitable clamp 95 on the standard 91. Several of these reciprocating tools can be carried inthe frame 75 by meansof other standards like 91, such as the one 96 shown at another point on the frame 76. Electric current is arranged to be continuously supplied to the reciprocating tool by means of a suitable flexible coniecting wire 97, which is connected to a suitable conducting strip 98 which is mounted on the frame 76 by means of suitable insulation and extends nearly the full length of the frame 76. Two spring clips, 99 and 100, join the terminals 100 and 102, which are mounted in the main frame by means of suitable insulation. The spring clips bear on the conducting strip, 98.

I will now describe an important feature of the apparatus which performs several objects: Mounted in the-main frame, 75, by means of suitable bearings 103, 104, 105 and 106, are the crank shafts 107 and 108 (Fig. 10) at the outer ends of which are secured arms 109, 110, 111 and 112, the free or outer ends of which carry rollers 118, 11st, 115 and 116, by means of suitable bearings and journals.

Each pair of arms, those on crank shaft 107, and those on the crank shaft 108, are operated and controlled by mechanism which is duplicate in every respect, so that, to save space, I have only shown one in section in Fig. 9. Hydraulic power is applied, as I believe it is the best, but those skilled in the art could probably use other means that would work well without departing from the nature of my invention. The frameworks containing the hydraulic operating cylinder, pump, and valves are as shown cast integrally with the frame 7 5. The plunger 117 being connected t-o the crank shaft 108by the connecting rod 118; the pump plunger 119 is operated by an eccentric cam 120 whichis secured to the shaft 121 to which is secured a gear wheel 122 which meshes with and is driven by the gear teeth on frame 70. and 12% indicate suitable valves common to all pumps. A valve 125 controls the fluid 'in the plunger cylinder, holding it, or re leasing it, as desired. 1 wish it understood that T have only undertaken to show the simplest operative apparatus for operating the arms, so as'to keep the drawings as simple as possible, and show my invention. Good self-contained hydraulic pumps, plungers, valves etc, are now on the market, and those skilled in the art can apply them to my apparatus without departing from the nature of my invention.

Theparts 126 and 127 as indicated by the dotted lines, are feet that may be attached to the frame75 when the apparatus is used for cutting sections from the floor of the mine.

The operation of the apparatus is as follows: The apparatus being placed in LlOSl? tion, power is applied to the arms 109, 110, 111 and 112, forcing them up tightly against the roof, serving the double purpose of supporting the section to be cut out and anchoring the apparatus against vibration. The channeling tools are then started and the frame 76 started to revolving around the frame 75. This action with the feeding of the channeling tools in their angular position will result in the cutting out of the material of the roof, of a practically perfect cone shaped section, and by means of the adjustments shown, any angle of cone desired may be obtained, and by means of suitable gages the feeding of the channeling tools can be stopped. lVhen the desired height of cone has been attained, the pressure of the arms can then be eased, which will ordinarily result in the section being severed of its own weight at the weakest point. If in some material the breaking does not Occur by the weight of the cone, a heavy breaking strain can be applied by releasing one pair of arms slightly and putting further pressure on the other pair of arms. If still further pressure is desired, a wedge can be applied in the channel at the side next the released arms, and power can even be applied to this wedge by putting a blunt tool on one of the channeling plungers and hitting the wedge with it. As soon as the section is severed the controlling valves, as 125 Fig. 9, are opened as desired by the operator, and the section will drop to the floor at a speed corresponding to the size of the openings made for the escaping fluid. lVhen the section is dropped to the floor as indicated by dotted lines in Fig. 9, the apparatus is moved to a. new position. It is to permit this that the frames 75 and 76 are made with gaps, which, when placed in proper relation, leaves an open side to the whole apparatus. A convenient hook as 128 may be formed on the frame 75, to hitch a rope or other suitable pulling means to, to move the apparatus.

I wish to call particular attention to the fact that sometimes the roofs or floors of mines consist of material which, while strong, such as some slates, may still be most rapidly cut by rotary cutters, in which case some simple form of cutting tools well known tb those skilled in the art can be applied in place of the percussion cutters shown, and proper feed similar to that shown being applied, the revolving action of the frame 76 will produce the same shaped section as the percussion cutters.

Referring now to Figs. 12, 13 and 14, which are respectively end, side and top views, and which show suitable apparatus for facilitating the removal of wedge or pyramid shaped sections from the roof of the mine, or from the floor by simple modification in mounting. 130 and 131 indicate suitable drill or percussion tool frames, on which are mounted suitable tool mechanisms, either compressed air or electricity, of well known construction, good ones of both kinds now being on the market, so no detailed description of these parts is thought necessary. The drill frame 130 by means of a suitable bracket, 132, is pivoted in the frame 133 by means of suitable pin 134, and frame 133 is pivoted in frame 135 by means of a suitable pin 136.

A bracket 146 concentric with the pin 136 is attached t the frame 133 and slides through a lug 147 on the frame 135. It can be rigidly secured to the lug by means of a set screw 148. The apparatus just described mounted on frame 135 is complete and self-contained, and will operate in any position it is placed.

Mounted on the frame 133 is a motor 137 the frame-work of which by means of suitable bracket-s, carries a crank shaft which is provided with suitable bearings in the brackets. Secured to the crank shaft 138 is a worm gear 139 which meshes with and is driven by a suitable worm 140, secured to the motor shaft 141. Pivotally attached to the drill frame 130 by means of suitable pin 142, is a bracket 143 provided with a bearing to receive the connecting rod 144, which is connected to the crank shaft 138, the connecting rod 144, is slidably adjustable in the bracket 143 and can be held rigidly where desired by means of the suitable sct screw 145.

The drill bracket 131 is pivotally mounted in the frame 149 by means of suitable bracket 150 and pin 151. A bracket 152 concentric with the pin 151 is attached to the drill frame 131 and slides through a lug 153 on the frame 149.

A set screw 154 holds the bracket 152 in such position as desired in the lug. The frame 149 is slidably mounted on a bar 155 which is provided with suitable rack teeth. The frame 149 by means of suitable bearing 156 and shaft 157 carries a rack pinion 158, it being secured to the shaft 157 and meshing with the rack bar 155. The rack pinion 158 may be suitably driven to feed the frame 149 along the rack by means of the feed mechanism of the drill; which, as shown, is driven by a revolving shaft 159 in the drill frame 131, a suitable extensible shaft 160 provided with universal couplings serving to connect the drill feed shaft 159 with the rack pinion shaft 157.

The rack bar 155 is supported at one end in the frame 135 resting in a slot in the frame. The bar is slidable through the slot, and can be held at any point desired by the set screw 163. The other end of the rack baris carried in the frame 161 which is practically the same as frame 135 except that it has two slots placed at right angles toone another, one for receiving the rack bar 1 :and the other for receiving a plain bar 162. Both bars can be secured in place in the frame 161 by means of set screws 163 and 164. The frame 161 is adapted to receive a drill or channeling apparatus in every respect similar to the one described on frame 135,- except that it would be oppositehanded, that is in practice if frame 135 was called right hand, frame 161 wouldbe called left hand. The plain bar 162 is also supported by the frame 165 which is a duplicate in every way of frame 161 except it is opposite handed. I Placed parallel to rack bar .155 of which. it isa duplicate, is the rack bar 166, with one end resting in frame 165 and theother end resting in frame 167, which is an exact duplicate of frame 135 described, except that the bracket or lug 168 which corresponds to bracket 147 on frame 135 is opposite handed. The rackbar 166 carries the frame 169 which is an exact duplicate of frame 149 on rack bar 155. .170 is a brace bar, having a slot formed at eachzend to engage the ends of the rack bars, 155 and 166. It will be seen that the tw rack bars 155 and 166 with the plain bar 162 and the brace bar 170, thus form an adjustable frame, rectangular or square, according to the way it isadjustecLthat provision is made for four drilling or channelingmechanisins, adjustable from vertical to any angular position required, and adjustably power fed through any are required, and for tw drilling or channeling mecha nisms adjustablecfrom vertical to any angular positionrequired, and power fed laterally.

Figs. 15 and 16are diagrammatic views, end and side, to show the application in cuttinga wedge shaped section, and Figs. 17 and 18 are diagrammatic views to show the application in cutting a pyramid shaped section.

I wish it-understood that the mechanism shownzin Figs. 9.and .10 forholding, breaking-and lowering the cone shaped sections,

may also :be used with this apparatus for holding, breaking and. lowering the wedge or pyramid shaped sections. I have not shown it=in connection with Figs. '12, .13 and 14 as it could easily be applied byrthose skilled in the art.

The brace bar 170 can be easily and quickly removed and thus without distur ing any of the rest of the mechanism, the apparatusmay bemoved away from thesection as 171, Fig. 14, which will pass through theopen space left by the removal of the brace .bar.

It is obvious that manyichanges can be fore do not wish :to be confined to the exact constructlon shown, but having shown the nature of my invention, and an operative form thereof, what I claim as new and of my own invention, is:

1. The method of mining consisting in dislodgi'ng from its native bed in the mine chamber a section of material of predetermlned shape and of a height corresponding to the distance between the floor and roof of tive bed in a minechamber, a section'of a height corresponding in its out position to the dlstancebetween floor and roof of-sald chamber at a predetermined pomt in their .cut positions, and moving said section to said point to support the roof of said chamber.

'3. The method of mining which consists in cutting a kerf around a mass of material forming a part of the roof of a mine chamber, dislodging such cut mass to have a height predetermined while such mass is still integral with the body from which it was removed, and then moving the .dislodged mass intact as'a solid block of shape and size as predetermined away from its place of dislodgment to a positionin the mine chamber toact as a prop between the fioor and roof thereof.

4. Themethod of mining which consists in operating in a mine chamber to bodily carve out from material in its native bed, a tapering section to have a height predetermined before removal from its original position, and moving such tapered section intact as a solid integral block as predetermined into position to act as-a support forthe roof ofsaid mine chamber.

5. The method of 'mining consisting in carving outtapering sections from material inits native bed adjoining amine chamber, and placing said sections in-position tosupport the roof of said chamberin such a manner as to form a series of double arches :be-

height between the floor and roof of said -m1ne chamber at a place spaced from said place of dislodgment, and movingsuch dislodged mass into position between the floor and roofto act as a roof prop at such place.

7. The method of mining consisting in bodily carving out from the material in its nativebed adjacent a mine chamber, tapering shaped sections of a size predetermined -in1their cut positions before removal, and

placing said sections in position to support the roof of said chamber with their bases resting on the floor and their points against the roof.

8. The method of mining which consists in dislodging a frustum from solid material in a mine chamber such frustum intact being of a height predetermined before dislodgment, and moving the dislodged frustum to a place spaced from the place ofdislodgment to act as a prop in the mine chamber.

9. The method of mining which consists in dislodging from its native bed in a mine chamber a mass of material of a predetermined shape and of a height corresponding approximately to the distance between the floor and roof of the mine chamber, and then sliding the dislodged mass of material over the floor of the mine chamber into position to act as a prop between the floor and roof of the mine chamber in a position spaced from the place 01 dislodgment.

10. The method of mining which consists in dislodging from the roof of a mine chamher a mass of material oi a predetermined shape and of a height corresponding to the distance between the floor and the roof of a mine chamber, such mass of material being approximately flat on its bottom and larger than at its upper end, so that when such mass falls to the floor the air under such larger bottom will cushion the fall and prevent it from breaking, and moving the dislodged section intact by sliding the same over the mine floor into position to act as a roof prop in the mine chamber.

11. The method of mining which consists in kerf-cutting about a mass of material in its native bed in a mine chamber and efiecting the dislodgment thereof so as to have a predetermined height corresponding to the distance between the floor and roof of the mine chamber, and moving such dislodged mass of material into position to act as a roof prop in the mine chamber. 7

12. The method of mining which consists in cutting a frusto-conical kertE about a mass of material in its native bed and effecting the dislodgment of such mass bounded by said kerf, and moving such mass intact into position to act as a roof prop in the mine chamber.

13. The method of mining which consists in carving out tapering shaped sections from material in its native bed forming the roof of a mine chamber, by kerf-cutting about said tapering shaped sections, then applying force to break oil the tapering sections after such cutting has extended to predetermined depths, to secure props of heights substantially equal to the distance between the floor and roof of the mine chamber where the props are to be located, and subsequently moving the dislodged tapering shaped sections each intact away from the places of dislodgment into positions to act as solid integral roof props in the mine chamber.

14:. The method of mining which consists in dislodging from their native beds in a mine chamber a: series of tapering sections of material each of approximately the height between the floor and roof of the mine chamber, and after dislodging such tapering sections moving them into positions respectively between the places ofdislodgment to form a series of roof props alternating with said places of dislodgment to form a series of double arches between the floor and roof of the mine chamber.

15. The method of mining consisting of bodily carving out from material in its native bed in a mine chamber, sections each of a shape and size predetermined in its out position before removal and so as to fit as a solid integral mass between the floor and roof of a mine chamber at predetermined locations, and placing said sections respectively in such predetermined locations each intact to serve as a solid support for the roof of the mine chamber to prevent subsidence thereof.

16. The method 01? mining which consists of dislodging solid sections of rock in a coal mine chamber, each section of a size and shape predetermined in its out position before removal, and placing said sections of rock respectively in position while maintaining them intact to form solid and continuous supports for the roof of a mine chamber in substitution of the coal pillars and to prevent the root from subsiding so that the coal pillars may be removed.

17. The method of mining consisting in dislodging sections of rock in a coal mine chamber, each section having upper and lower bearing surfaces and each section being of a predetermined shape and size for the formation of a continuous solid support between the floor and the roof of the mine chamber to sustain the latter in place of coal pillars to be removed, and placing said sections respectively in position while remaining intact to solidly support the roof of said chamber from the floor and prevent subsidence of such roof while and after coal pillars are being removed.

18. The method of forming roof props from the roof of a mine chamber, which consists in dislodging a: tapering section of solid material from such roof having a large fiat bottom compared to its total weight, causing such dislodged section to drop from such roof to the fioor while the air under such section cushions such fall and prevents the breaking to pieces of such section, such section being of a predetermined height corresponding to the height between the floor and the roof of the mine chamber at the place where such section is to be located, and moving said section to such place to act as a solid integral roof prop between the floor and roof of the mine chamber.

19. The method of mining which consists in producing a plurality of intersecting plane kerfs in solid material in the mine chamber to effect the dislodgment of a body of material of a height predetermined before dislodgment, and moving the dislodged body of material intact to a position spaced from the place of dislodgment to act as a roof prop in the mine chamber. v

20. The method of mining which consists in producing a plurality of plane kerfs comprising kerfs in intersecting planes to effect the dislodgment of a solid body of material in the mine chamber, and moving such solid body of material intact to a position spaced from the place of dislodgment to act as a prop in the mine chamber.

21. The method of mining which consists in producing a plurality of plane kerfs in the solid material in the mine chamber comprising kerfs in intersecting planes on opposite sides of the body of material to be dislodged and spaced apart upright parallel kerfs at the ends of the material to be dislodged, and moving the dislodged body of material intact from the place of dislodgment to a position in the mine chamber where it can serve as a roof prop.

22. The method of mining which consists in dislodging from solid material in a mine chamber a body of material inverted V-shaped in cross section and having flat ends, the height of such dislodged body of material being predetermined before dislodgrnent, and moving the dislodged body of material intact from the place of dislodgment to a position where it can serve as a solid prop between the floor and roof of the mine chamber.

23. The method of mining which consists in cutting inclined kerfs in the roof of the mine chamber in converging intersecting planes and in cutting spaced-apart, upright kerfs in approximately parallel planes to effect the dislodgment from the roof of a tapering section of a height predetermined before dislodgment and having upright flat ends and inclined fiat sides, and moving the dislodged body of material intact from the place of dislodgment to a position where it can serve as a solid support throughout its height and to solidly support the roof of the mine chamber from the floor thereof and prevent subsidence of such roof while and after coal pillars are being removed.

In testimony whereof I have signed my name to this specification.

EDMUND C. MORGAN. 

